The evolutionary and ecological role of heat shock proteins

TLDR

Heat shock proteins act as molecular chaperones that aid organisms in coping with internal and external stress, with up‑regulation promoting protein folding and degradation, and research has largely focused on the Hsp70 family, which plays key roles in stress resistance. The authors review evidence linking stress resistance to inducible Hsp expression, examine factors that trigger the heat shock response and their costs, discuss the ecological and evolutionary relevance of Hsps to life‑history traits, and propose future genomic and proteomic studies to deepen understanding. The review synthesizes evidence on stress resistance, characterizes factors that induce the heat shock response and their costs, and discusses studies on mild stress, high larval densities, inbreeding, age, and natural variation in Hsp expression.

Abstract

Abstract Most heat shock proteins (Hsp) function as molecular chaperones that help organisms to cope with stress of both an internal and external nature. Here, we review the recent evidence of the relationship between stress resistance and inducible Hsp expression, including a characterization of factors that induce the heat shock response and a discussion of the associated costs. We report on studies of stress resistance including mild stress, effects of high larval densities, inbreeding and age on Hsp expression, as well as on natural variation in the expression of Hsps. The relationship between Hsps and life history traits is discussed with special emphasis on the ecological and evolutionary relevance of Hsps. It is known that up‐regulation of the Hsps is a common cellular response to increased levels of non‐native proteins that facilitates correct protein folding/refolding or degradation of non‐functional proteins. However, we also suggest that the expression level of Hsp in each species and population is a balance between benefits and costs, i.e. a negative impact on growth, development rate and fertility as a result of overexpression of Hsps. To date, investigations have focused primarily on the Hsp70 family. There is evidence that representatives of this Hsp family and other molecular chaperones play significant roles in relation to stress resistance. Future studies including genomic and proteonomic analyses will increase our understanding of molecular chaperones in stress research.